Active filter device and electric compressor comprising same

Abstract

Provided is an active filter device capable of effectively reducing common mode noise and differential mode noise and optimizing filter characteristics. The active filter device includes an inverting amplifier circuit 37 that inverts and amplifies a common mode voltage and a differential amplifier circuit 64 that differentially amplifies a differential mode voltage, and an output voltage of the inverting amplifier circuit 37 is applied as a common mode compensation voltage to Y capacitors 21, 22 , an output of the differential amplifier circuit 64 obtained by amplifying a voltage of a positive-side power supply line 11 is applied as a differential mode compensation voltage to a negative-side X capacitor 42 , and an output of the differential amplifier circuit 64 obtained by amplifying a voltage of a negative-side power supply line 12 is applied as a differential mode compensation voltage to a positive-side X capacitor 41.

The invention claimed is: 
     
         1 . An active filter device comprising:
 a common mode choke coil inserted into a pair of positive-side and negative-side power supply lines;   a normal mode choke coil connected to the pair of power supply lines or one of the power supply lines;   a detection unit that detects voltages of the pair of power supply lines;   an inverting amplifier circuit that inverts and amplifies a common mode voltage detected by the detection unit;   a Y capacitor connected between an output of the inverting amplifier circuit and the pair of power supply lines;   a differential amplifier circuit that differentially amplifies a differential mode voltage between the pair of power supply lines, which is detected by the detection unit; and   an X capacitor connected between an output of the differential amplifier circuit and the pair of power supply lines,   wherein an output voltage of the inverting amplifier circuit is applied to the Y capacitor, and   an output voltage of the differential amplifier circuit obtained by amplifying the voltage of the positive-side power supply line is applied to the X capacitor connected to the negative-side power supply line, and an output voltage of the differential amplifier circuit obtained by amplifying the voltage of the negative-side power supply line is applied to the X capacitor connected to the positive-side power supply line.   
     
     
         2 . The active filter device according to  claim 1 , wherein
 the differential amplifier circuit includes a positive-side amplifier having a non-inverting input terminal to which the voltage of the positive-side power supply line detected by the detection unit is input as a differential input signal, and a negative-side amplifier having a non-inverting input terminal to which the voltage of the negative-side power supply line detected by the detection unit is input as a differential input signal, and   the X capacitor connected to the negative-side power supply line is connected to an output of the positive-side amplifier, and the X capacitor connected to the positive-side power supply line is connected to an output of the negative-side amplifier.   
     
     
         3 . The active filter device according to  claim 1 , wherein a voltage detected by a single detection unit including a pair of voltage detection capacitors is input to the inverting amplifier circuit and the differential amplifier circuit. 
     
     
         4 . The active filter device according to  claim 1 , wherein the detection unit is provided for each of the inverting amplifier circuit and the differential amplifier circuit. 
     
     
         5 . The active filter device according to  claim 1 , wherein a ground path of the detection unit and a ground path of the inverting amplifier circuit are separately connected to a circuit ground. 
     
     
         6 . An electric compressor comprising: the active filter device according to  claim 1 ; and an inverter device, wherein the active filter device and the inverter device are provided integrally with a housing. 
     
     
         7 . The electric compressor according to  claim 6 , wherein the housing has a ground potential, and the circuit ground is connected to the housing, and the ground path of the detection unit is connected to the housing, and the ground path of the inverting amplifier circuit is connected to the circuit ground.